Said they were Telstra and unusual activity from my internet connection. As it was a mobile number with background noise of a telecentre most likely scam

Called no voicemail left

Called and left a voice message. Couldn’t understand what they were saying.

Scam, number not connected

I didn't answer the unknown number, they called twice seconds apart. No voicemail was left.

I didn’t answer as unknown number and no message left. Probable scam call.

They say they are from telstra nbn broadband technicians

Scam - number not connected